Why do anxiety symptoms begin?

There are usually a combination of causes.Two of the important ones are:

1  The amount of stress you are under:

You may have a single major problem,or more likely a number of smaller problems which all add up to a large amount of stress.Stress can be measured to some an extent by the amount of changes that have taken place in your life recently.Being physically tired,run down and having many changes or traumas makes you more vulnerable to anxiety.
2  The kind of person you are :

Some people have a more sensitive emotional nervous system.Their bodies' arousal response might be triggered more quickly and take a longer time to calm down.Some people have learned from their parents in their early experiences how to get anxious and how to worry.

What maintains anxiety?

Why does anxiety stay with you? What keeps it going? Basically, there seem to be two reasons:

1 Because of the way you behave,especially because you avoid the situations you fear.
2 Because of beliefsyou have about the situation and its consequences.
Let us look at some examples:
'Lift phoebic' people never go in a lift because they may believe it will fall to the bottom of the lift shaft ;' agoraphobics' never go out because they may believe they will collapse and die of heart attack; some people may avoid meeting others because they believe that in a disagreement,they will love their temper and hit people; some people obsessively check the locks on the doors and windows over and over before going to bed because they are certain that burglars will break in.
These examples make clear two things:
1-There may be an exaggerated,irrational belief (and the person may realise that it is just that) about what will happen in the feared situation.
2-There is an avoidance of the feared situation,which,of course,allows the irrational belief to continue because it is never proved.